The purpose of this study is to evaluate the renal proximal tubule Na-H exchanger in rats adapted to the chronic states of potassium depletion, hypercapnea and metabolic acidosis to determine if the altered urinary acidification process observed in these conditions is associated with an intrinsic mocification of this transport mechanism. We will isolate and purify brush border membrane visicles from renal cortex of rats undergoing adaptation to each of the chronic conditions. The effects of imposed pH gradients and of the diuretic Amiloride on Na+ flux will be determined in membranes from control and experimental animals. The changes in Na-H exchange will be characterized further with respect to cation specificity, saturation kinetics for Na+ and inhibitor sensitivity. If a change in Na-H exchange is observed in any experimental group, brush border membranes will be analyzed for possible associated alterations in lipid composition. Radiolabelled precursors of phospholipid and protein will be given to animals, and incorporation of isotope into brush border membranes will be studied to determine altered rates of phospholipid and protein synthesis respectively. This study should provide important information regarding adaptation on the subcellular level with respect to membrane transport and structure.